Source-separated Urine Research Articles

Fate of Extracellular DNA in the Production of Fertilizers from Source-Separated Urine.

The practice of urine source-separation for fertilizer production necessitates an understanding of the presence and impact of extracellular DNA in the urine. This study examines the fate of plasmid DNA carrying ampicillin and tetracycline resistance genes in aged urine, including its ability to be taken up and expressed by competent bacteria. Plasmid DNA incubated in aged urine resulted in a >2 log loss of bacterial transformation efficiency in Acinetobacter baylyi within 24 h. The concentration of ampicillin and tetracycline resistance genes, as measured with quantitative polymerase chain reaction, did not correspond with the observed transformation loss. When the plasmid DNA was incubated in aged urine that had been filtered (0.22 μm) or heated (75 °C), the transformation efficiencies were more stable than when the plasmids were incubated in unfiltered and unheated aged urine. Gel electrophoresis results indicated that plasmid linearization by materials larger than 100 kDa in the aged urine caused the observed transformation efficiency decreases. The results of this study suggest that extracellular DNA released into aged urine poses a low potential for the spread of antibiotic resistance genes to bacteria once it is released to the environment.

Performance Characterization of a Steam Distillation Process for Ammonium Recovery from Urine

AbstractThe purpose of this study was to characterize the nitrogen recovery efficiency of a full-scale prototype nutrient recovery system that processes source-separated urine by the steam distilla...

The recovery of phosphorus from source-separated urine by repeatedly usable magnetic Fe3O4@ZrO2 nanoparticles under acidic conditions

The separation of urine at source for phosphorus (P) recovery is attractive taking into account the high P concentration and small volume. However, the treatment of urine is still challenging due to its unpleasant odor and hygiene problems. Because the above problems could be solved by acidification to keep the pH of urine below 4, we propose a novel strategy to recover P from acidified urine using tailored hydrous zirconia-coated magnetite nanoparticles (Fe3O4@ZrO2). This strategy involves the selective adsorption of phosphate by easily separable and reusable Fe3O4@ZrO2, the desorption of adsorbed phosphate, and the precipitation of desorbed phosphate as calcium phosphate fertilizer. The results indicated that at pH 4, the P in synthetic urine was selectively adsorbed and could be exhausted using Fe3O4@ZrO2. Nearly all (>97.5%) of the sequestered P on the Fe3O4@ZrO2 nanoparticles was stripped using ≥1 M NaOH solution and ~100% of the stripped P was then successfully transformed into calcium phosphate, upon adding CaCl2 at pH >12 and a Ca/P molar ratio of 3. The liquid/solid (Fe3O4@ZrO2 particles) mixture could be conveniently separated for reuse using an external magnetic field. The reusability of the Fe3O4@ZrO2 nanoparticles in the extraction of P from synthetic urine was confirmed using five cycles of the adsorption-desorption process and their performance validated using real urine samples. The mechanism of phosphate adsorption was investigated using XPS, FTIR and zeta potential measurements, showing that phosphate was chemically adsorbed on the surface through direct coordination to zirconium atom via ligand exchange.

Efficient removal of phosphate from acidified urine using UiO-66 metal-organic frameworks with varying functional groups

The removal of phosphate from source-separated urine is an efficient approach to reduce the P-load in receiving waters due to its high P concentration and low volume in wastewater. However, a highly efficient adsorbent is imperative for this purpose. Metal-organic frameworks (MOFs) have recently attracted a lot of attention in adsorption due to their outstanding physicochemical features. In this study, we examined four Zr-based MOFs (UiO-66, UiO-66-NO2, UiO-66-Br and UiO-66-NH2) for the adsorption of phosphate from acidified urine. Our results indicated that the zirconium content, pore size and crystallinity are driving forces for the adsorption process. UiO-66-NH2 displayed the highest adsorption capacity (153.9 mg/g) at 25 °C and pH 4. Phosphate in urine could be nearly totally depleted (>99% removal) using UiO-66-NH2 at a dosage ≥13.5 g/L. Elevating temperature and lowering pH are effective strategies to enhance the adsorption performance. The reduction of the isoelectric point of UiO-66-NH2 after P uptake, the activation energy of the adsorption process estimated using Arrhenius equation (63.1 kJ/mol), FTIR spectroscopy and XPS suggested that inner-sphere complexation between phosphate and Zr atoms in the MOFs was the key adsorption mechanism. The performance of adsorption-desorption-regeneration using real human urine was verified.

Effect of reactor configuration on the kinetics and nitrogen byproduct selectivity of urea electrolysis using a boron doped diamond electrode

Electrochemical systems have emerged as an advantageous approach for decentralized management of source-separated urine with the possibility of recovering or removing nutrients and generating energy. In this study, the kinetics and byproduct selectivity of the electrolytic removal of urea were investigated using a boron doped diamond working electrode under varied operational conditions with a primary focus on comparing undivided and divided reactors. The urea removal rate in the undivided and divided reactors was similar, but the divided reactor had an increased required cell voltage needed to maintain the equivalent current density. The current efficiency was similar for 0.1, 0.25, and 0.5 A (33.3, 83.3, 167 mA/cm2), suggesting no interference from competing reactions at higher potentials. In a divided reactor, increasing the anolyte pH reduced the urea removal rate presumably from hydroxyl radical scavenging by hydroxide. Further, for all divided reactor experiments, the final pH was less than 1, suggesting that the transport of protons across the ion exchange membrane to the cathode was slower than the oxidation reactions producing protons. The nitrogen byproduct selectivity was markedly different in the undivided and divided reactors. In both reactors, nitrate (NO3−) formed as the main byproduct at the anode, but in the undivided reactor it was reduced at the stainless steel cathode to ammonia. In the presence of 1 M chloride, the urea removal kinetics improved from the generation of reactive chlorine species, and the byproduct selectivity was shifted away from NO3− to presumably chloramines and N2. Overall, these results indicate that the electrochemical reactor configuration should be carefully considered depending on the desired outcome of treating source-separated urine (e.g., nitrogen recovery, H2 generation).

Identifying and Overcoming Rate-Limiting Steps for Nitrogen Fertilizer Production from Urine

Wastewaters containing nitrogen have a deleterious impact when discharged to the environment. Conventional nitrogen removal techniques are resource-intensive and limited to settings with formal sewer infrastructures. Furthermore, these techniques treat nitrogen as an impurity to remove rather than a resource to recover. In 2018, we addressed all three of these issues by demonstrating a proof-of-concept for electrochemical stripping (ECS) of ammonium sulfate from source-separated urine. ECS does not require caustic chemicals, can be implemented in remote settings, and recovers the fertilizer ammonium sulfate. In 24 hours, our ECS setup achieved 93% nitrogen recovery. Our next step is to improve the time-efficiency of ECS, but because it is a novel technology, we lack guidance in the literature for optimal experimental ranges. To grasp a more mechanistic understanding of the steps bottlenecking nitrogen recovery, we develop a model as follows. First, we decompose nitrogen recovery into major transport and chemical transformation steps. Experimental data is then fit to the model with a goodness of fit test. Using these fitted values as a starting point, we perform sensitivity analyses for each major step in order to elucidate what parameters most crucially govern nitrogen recovery. Preliminary results (attached) suggest that ammonia volatilization contributes nontrivial nitrogen losses to the system. Our model will guide further developments of ECS technology by providing quantitative measures of how to overcome rate-limiting steps in nitrogen recovery. Figure 1

Three-stage treatment for nitrogen and phosphorus recovery from human urine: Hydrolysis, precipitation and vacuum stripping

Source separation of human urine has not been widely adopted because of scaling on urine collecting fixtures and lack of verified technologies for on-site utilization of waterless urine. This study investigated the effects of flushing liquid, temperature and urease amendment on hydrolysis of urea to ammonia, explored ammonia recovery via vacuum stripping in connection with phosphorus recovery via struvite precipitation in different sequences, and performed economic analysis of a proposed nutrient recovery strategy. It was found that acetic acid could be dosed at 0.05–0.07 N to flush urine-diverting toilets and urinals for hygiene and prevention of scaling. However, a high dosage of 0.56 N completely inhibited urea hydrolysis. Source-separated urine could be stored at 25 °C with ample urease for complete urea hydrolysis within approximately 20 h. Fully hydrolyzed waterless urine contained 9.0–11.6 g/L ammonia-N, 0.53–0.95 g/L phosphate-P and only 2.3–9.1 mg/L magnesium. When magnesium was supplemented to attain the optimum Mg2+: PO43− molar concentration ratio of 1.0 in hydrolyzed urine, batch operation of a pilot-scale air-lift crystallizer removed 93–95% of phosphate and produced 3.65–4.93 g/L struvite in 1–5 h. Batch operation of a pilot-scale vacuum stripping – acid absorption system for 12 h stripped 72–77% of ammonia and produced 37.6–39.7 g/L (NH4)2SO4. Compared with the ammonia → phosphorus recovery sequence, the struvite precipitation → vacuum stripping sequence produced more struvite and ammonium sulfate. The strategy of urea hydrolysis → struvite precipitation → vacuum stripping of ammonia is a sustainable alternative to the conventional phosphorus fertilizer production and ammonia synthesis processes.

P-recovery in a pilot-scale struvite crystallisation reactor for source separated urine systems using seawater and magnesium chloride as magnesium sources

Practical recovery of a non-renewable nutrient, such as phosphorus (P), is essential to support modern agriculture in the near future. The high P content of urine, makes it an attractive source for practicing the recovery of this crucial nutrient. This paper presents the experimental results at pilot-plant scale of struvite crystallisation from a source-separated urine stream using two different magnesium sources, namely magnesium chloride and seawater. The latter was chosen as sustainable option to perform P-recovery in coastal areas. Real seawater was used to assess in a more realistic way its efficiency to precipitate P as struvite, since its composition (with noticeable concentration of ions such as Ca2+, SO42−, Na+, …) could lead to the formation of impurities and other precipitates. 0.99 g of struvite was obtained per litre of urine irrespective of the operational conditions tested. In all tested conditions, precipitation efficiencies exceeded 90% and recovery efficiencies were higher than 87%, with an average struvite crystal size higher than 110 μm (and up to 320 μm, depending on the experimental conditions) in the harvested struvite samples. Almost pure struvite was obtained when MgCl2 was used as precipitant, while amorphous calcium phosphate and other impurities appeared in the precipitates using seawater as magnesium source. However, the lower settling velocity of the amorphous precipitates in comparison with the struvite precipitates suggests that their separation at industrial scale could be relatively straightforward.

Efficient nutrient recovery/removal from real source-separated urine by coupling vacuum thermal stripping with activated sludge processes

Separation and treatment of human urine from domestic wastewater have been recognized as a sustainable alternative to conventional urban sanitation system, but the unique water quality of source-separated urine, such as high nutrient, insufficient alkalinity and low COD/nitrogen ratio, poses challenges to the biological nitrogen removal process. It was hypothesized that a physicochemical pre-treatment should be adopted to not only reduce nitrogen load but adjust water quality suitable for biological treatment. In this study, a vacuum thermal stripping process coupled to acid absorption was used as a pre-treatment to recover ammonia from hydrolyzed urine in the form of ammonium sulphate. The maximal ammonia mass transfer coefficient of 17.6 mm/h was obtained under 60 °C and 21.3 kPa 80% of the nitrogen in hydrolyzed urine was recovered in 3 h batch stripping experiments without pH adjustment, corresponding to a nitrogen recovery loading rate of 36 kg N/m3⋅d. The majority of organic matters were retained in urine solutions, thus COD/N and alkalinity/NH4+N ratios were elevated to 4.75 and 4.37, respectively. Phosphorus recovery could be simultaneously obtained in stripping process by adding MgCl2. The remaining nitrogen was effectively removed via short-cut nitrification and denitrification in an anoxic/oxic membrane bioreactor. More than 95% of overall nutrient recovery/removal from urine was achieved with a minimal consumption of external resources. The economic assessment of the technique showed that the recovery/removal of nutrients from 1 m3 of urine can make a profit of € 0.26.

Source-Separated Human Urine as Fuel for Microbial Fuel Cell: A Mini Review

Source-Separated Human Urine as Fuel for Microbial Fuel Cell: A Mini Review

Factors Affecting the Crystal Size of Struvite-K Formed in Synthetic Urine Using a Stirred Reactor

The crystallization of struvite-K (MgKPO·6HO) can simultaneously recover phosphate and potassium from source-separated urine. However, its crystal size has been rarely reported despite significantly affecting the crystallizer performance. Experimental results show that the average size of struvite-K was 15-63 μm in ammonium-depleted synthetic urine under the examined conditions with a stirred reactor. A low supersaturation ratio (S) or the same S induced by low pH and high Mg:P ratio resulted in large crystal size. Large crystals also formed at high agitation speed, small feed volume, or feeding close to the stirring impeller. The size distribution of struvite-K crystals was predicted using the coupling resolution of the population balance equation to on-site turbidity measurement. The estimated kinetic parameters quantitatively described the nucleation and crystal growth of struvite-K under different conditions of supersaturation, feeding, and mixing. This work proposes approaches to obtain large crystals while reducing fines of struvite-K.

Membrane stripping enables effective electrochemical ammonia recovery from urine while retaining microorganisms and micropollutants

Ammonia recovery from urine avoids the need for nitrogen removal through nitrification/denitrification and re-synthesis of ammonia (NH3) via the Haber-Bosch process. Previously, we coupled an alkalifying electrochemical cell to a stripping column, and achieved competitive nitrogen removal and energy efficiencies using only electricity as input, compared to other technologies such as conventional column stripping with air. Direct liquid-liquid extraction with a hydrophobic gas membrane could be an alternative to increase nitrogen recovery from urine into the absorbent while minimizing energy requirements, as well as ensuring microbial and micropollutant retention. Here we compared a column with a membrane stripping reactor, each coupled to an electrochemical cell, fed with source-separated urine and operated at 20 A m−2. Both systems achieved similar nitrogen removal rates, 0.34 ± 0.21 and 0.35 ± 0.08 mol N L−1 d−1, and removal efficiencies, 45.1 ± 18.4 and 49.0 ± 9.3%, for the column and membrane reactor, respectively. The membrane reactor improved nitrogen recovery to 0.27 ± 0.09 mol N L−1 d−1 (38.7 ± 13.5%) while lowering the operational (electrochemical and pumping) energy to 6.5 kWhe kg N−1 recovered, compared to the column reactor, which reached 0.15 ± 0.06 mol N L−1 d−1 (17.2 ± 8.1%) at 13.8 kWhe kg N−1.Increased cell concentrations of an autofluorescent E. coli MG1655 + prpsM spiked in the urine influent were observed in the absorbent of the column stripping reactor after 24 h, but not for the membrane stripping reactor. None of six selected micropollutants spiked in the urine were found in the absorbent of both technologies.Overall, the membrane stripping reactor is preferred as it improved nitrogen recovery with less energy input and generated an E. coli- and micropollutant-free product for potential safe reuse. Nitrogen removal rate and efficiency can be further optimized by increasing the NH3 vapor pressure gradient and/or membrane surface area.

Optimisation of a forward osmosis and membrane distillation hybrid system for the treatment of source-separated urine

The high concentration of nitrogen, phosphorous and potassium in human urine makes it a suitable raw material for fertiliser production. However, urine is often diluted with a significant amount of flushing water which increases the costs for the downstream nutrients recovery process. Re-using the water and the nutrients in the urine is paramount for enhancing the sustainability of our waste management system. In this work, a combination of forward osmosis (FO) and membrane distillation (MD) was used to extract distilled water from human urine. FO was chosen as MD pre-treatment to increase the overall nitrogen rejection and to prevent wetting of the MD membrane. The goal of this investigation was to tune the FO and MD operating parameters to reduce the nitrogen transport to the MD permeate. Urine pH, draw solution (DS) salt concentration and operating pressure were varied as a means to enhance the FO performances. On the other hand, feed temperature, nitrogen concentration and membrane characteristics were investigated to optimise the MD process. With 2.5 M NaCl as DS commercial FO membranes achieved a water flux between 31.5 and 28.7 L m−2 h−1 and a minimum nitrogen flux of 1.4 g L−1. An additional 33% reduction in the nitrogen transport was observed by applying minimal hydraulic pressure on the DS. However, this was also found to significantly reduce the net transmembrane water flux. Acidification of the feed was also beneficial for both FO and MD nitrogen rejection. Finally, we demonstrated that, by tuning the MD membrane porosity and thickness, higher MD permeate quality could be achieved. To conclude, the hybrid FO-MD process is expected to be an effective solution for the production of clean water and concentrated fertiliser from human urine. This double barrier separation process could be suitable for both water reclamation in space application and resource recovery in urban application.

Anaerobic ureolysis of source-separated urine for NH3 recovery enables direct removal of divalent ions at the toilet

Source-separated urine is of interest for nutrient recovery. Most nitrogen recovery technologies rely on ammonia (NH3) as input, which requires ureolysis. As urease positive bacteria are widespread, source-separated urine is unstable, not only leading to NH3 release but also loss, odor nuisance, and downstream scaling. Hence, ureolysis ideally occurs in a closed controlled environment close to the toilet. We characterized microbial-induced ureolysis, subsequent divalent cation precipitation, and fermentation in anaerobic sequencing batch reactors (SBRs) at 15 °C and 28 °C. Temperatures were a proxy for urine hydrolysis in a wet well at street level or in the toilet, respectively. The need for inoculation and the metabolic stability was assessed by inoculation with autofermented urine or a mixture of anaerobic digestion and fermentation sludge. The highest specific ureolysis rates in the SBRs were achieved at 28 °C: 2107 ± 395 and 1948 ± 1121 mg N g VSS−1 d−1, for the mixed and autofermented inoculum, respectively. For Ca2+ and Mg2+ precipitation, and organics fermentation, autofermented urine at 28 °C performed best with 47.9 ± 16.4 mg Ca2+ g VSS−1 d−1, 8.2 ± 4.6 mg Mg2+ g VSS−1 d−1, and 623 ± 129 mg VFA-COD g VSS−1 d−1, respectively. This indicates the hydrolysis reactor should be close to the toilet. The selected inoculum did not impact ureolysis, whereas both Ca2+ and Mg2+ precipitation and fermentation were better in the SBRs with autofermented urine. Ureolysis was identified as the only process significantly impacting the microbial community, indicating external inoculation would not be required. A urine hydrolysis reactor in the toilet without external inoculation could thus serve as a controlled environment to release NH3 and remove divalent cations to prevent scaling in downstream transport and processing. For practical implementation in a household toilet, the reactor should be designed for user-friendly precipitate discharge and odor control.

Removal of sulfonamide antibiotics and human metabolite by biochar and biochar/H2O2 in synthetic urine

Source-separated urine has been increasingly regarded as a promising alternative waste-stream for effectively removing pharmaceuticals and human metabolites. This study investigated the removal of sulfonamide antibiotics, one category among the most frequently detected antibiotics in the environment, by biochar and biochar/H2O2 in synthetic urine matrix. The adsorption and degradation of four parent sulfonamide antibiotics, including sulfamethoxazole, sulfadiazine, sulfamethazine, sulfadimethoxine, and one human metabolite, N4-acetyl-sulfamethoxazole (together referred as SAs) were investigated. Biochar derived from cotton straw was applied as adsorbent for SAs and catalyst for H2O2. Results showed that the adsorption of SAs was inhibited in urine compared with that in phosphate buffer solution. Bicarbonate in urine placed major influence. Langmuir isotherm model well described the adsorption process in both buffer and urine matrices. Adsorption and desorption rates were estimated by a kinetic model, which well fitted the removal of SAs from aqueous phase at various biochar doses. The adsorption of SAs on biochar was due to multiple forces, in which van der Waals forces and hydrophobicity played major roles in distinguishing the sorption behavior of different SAs. To destruct the SAs, H2O2 was added with biochar. Except for N4-acetyl-sulfamethoxazole, all the parent SAs can be degraded in urine matrix. Carbonate radical, produced from the activation of peroxymonocarbonate by biochar, was proposed to be the major contributing reactive species in biochar/H2O2 system in urine matrix.

Comparison of different K-struvite crystallization processes for simultaneous potassium and phosphate recovery from source-separated urine

Controlled K-struvite crystallization is an attractive technology to simultaneously recover phosphate and potassium from urine. This study investigated the recovery of phosphate and potassium from source-separated urine by K-struvite crystallization using different use models of low-grade MgO (LG-MgO): LG-MgO alone (model 1, M1), LG-MgO plus phosphorus acid (model 2, M2), and a pre-formed stabilizing agent by adding LG-MgO plus phosphorus acid (model 3, M3). Results showed that 100% phosphate and 25% K could be recovered from urine by M1. M2 at an MgO:K:P molar ratio of 4:1:1.6 provided a maximum P and K recovery efficiency at 100% and 70%. M3 achieved a same K-removal efficiency as M2, but the phosphate recovery efficiency was lower than that of M2 due to the dissolution of phosphate in the stabilizing agent. K-struvite crystallization was closely accompanied by severe co-precipitation of Na-struvite. Increasing the Na concentration markedly improved the ability of Na co-precipitation, but the variation of pH did not affect the competition precipitation of K and Na. When the Na:K molar ratio was >10, the precipitation of Na was more than that of K. A process performance evaluation indicated that M3 is more suitable for simultaneous K and P recovery from source-separated urine.

Field evaluation of the fertilizing potential of biologically treated sanitation products

Among different approaches of treating source-separated urine and feces for agronomic utilization, the treatment by addition of nitrifying bio-seeds seems to be useful in increasing the fertilizing potential of these sanitation products by modifying and stabilizing the nitrogen profile. In this study, biological treatment was applied to an onsite resource-oriented sanitation system by adding nitrifying microorganism bio-seeds. Further, the potential of the sanitation products to be utilized as fertilizer for white radish (Raphanus sativus var. longipinnatus) cultivation was examined and compared with that of a commercial fertilizer. This was done through the measurement of nutrients released in soil samples as well as measurements of root mass, root length, and the measurement of accumulated nitrogen, sugar, and water content in plant tissues. Our results show that soil fertilized with a mixture of biologically treated urine and feces exhibits a statistically similar nutrient release trend to soil fertilized using a commercial fertilizer. Moreover, soil fertilized with a mixture of biologically treated urine and feces yielded larger white radishes with a higher sugar and water content, as well as a higher accumulation of nutrients in the plant tissues, than soil fertilized with a commercial fertilizer.

Electrochemical Stripping to Recover Nitrogen from Wastewater

Electrochemical water treatment replaces chemical inputs with electricity, allowing for fine-tuning of unit processes through control of applied current and potential. These modular systems are flexible to varying degrees of centralization and robust to handle intermittent flows and shock loadings. Recovering nitrogen from separately collected urine can potentially reduce costs and energy of wastewater nitrogen removal and fertilizer production. Through benchtop experiments, we demonstrate the recovery of nitrogen from urine as ammonium sulfate using electrochemical stripping, a combination of electrodialysis and membrane stripping. Nitrogen was selectively recovered with 93% efficiency in batch experiments with real urine and required 30.6 MJ kg N–1 in continuous-flow experiments (slightly less than conventional ammonia stripping). The effects of solution chemistry on nitrogen flux, electrolytic reactions, and reactions with electro-generated oxidants were evaluated using synthetic urine solutions. Fates of urine-relevant trace organic contaminants, including electrochemical oxidation and reaction with electro-generated chlorine, were investigated with a suite of common pharmaceuticals. Trace organics (<0.1 mg L–1) and elements (<30 mg L–1) were not detected at appreciable levels in the ammonium sulfate fertilizer product. This novel approach holds promise for selective recovery of nitrogen from concentrated liquid waste streams such as source-separated urine, anaerobic digester effluent, and nitrogen-rich food waste.

Nitrogen Recovery With Source Separation of Human Urine—Preliminary Results of Its Fertiliser Potential and Use in Agriculture

The growing demand for food and the increasing costs of cultivation are posing a challenge for agriculture. Diminishing phosphorus reserves, as well as the energy intensive method of producing nitrogen fertilisers are drivers for more intensive reuse of different organic fertilisers, such as manures and excreta. Source separation and fertilisation with human urine can be one option for nutrient reuse. Urine contains all the main nutrients as well as micronutrients in soluble form, but it also contains chemicals, like pharmaceuticals and hormones. The aim of this study was to examine the efficiency and safety of the use of source separated human urine as a fertiliser for barley (Hordeum vulgare). The fertiliser efficiency of source-separated urine was examined in field-scale experiments for the first time in Finland. Two separate cultivation experiments in two fields and barley varieties were conducted. The efficiency of urine as a fertiliser was compared to corresponding amount of mineral fertiliser. No fertilizer was applied to one plot in order to create a reference treatment. The two experiments were conducted using variety Wolmari with 54 kg N ha-1 and variety Harbinger with 100 kg N ha-1. The barley grain and straw yield grown with urine fertiliser was equivalent to the yield in mineral fertilised plots. The growth of barley in both fertiliser treatments was slightly faster, compared to non-fertilised treatment. There were no significant differences between the treatments in terms of protein content of the grain although the results varied in terms of the thousand grain weight (TGW) and germination. The urine analyses indicated that there were no pathogen indicators, nor heavy metal concentrations, exceeding the limit values set by legislation. The main nutrient concentrations (N, P, K) would also meet the requirements for a fertiliser product according to Finnish legislation. Pharmaceuticals and hormones were found from the urine, but apart from progesterone, all of them presented extractable values in soil below the detection limits, and they were not detected in measurable amounts in barley grain at the end of the growing season. These results suggest that source separated urine could be an efficient fertiliser in crop cultivation.

Effect of Urine Compounds on the Electrochemical Oxidation of Urea Using a Nickel Cobaltite Catalyst: An Electroanalytical and Spectroscopic Investigation.

Cyclic voltammetry (CV) and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were used to investigate the effect of major urine compounds on the electro-oxidation activity of urea using a nickel cobaltite (NiCo2O4 ) catalyst. As a substrate, carbon paper exhibited better benchmark potential and current values compared with stainless steel and fluorine-doped tin oxide glass, which was attributed to its greater active surface area per electrode geometric area. CV analysis of synthetic urine showed that phosphate, creatinine, and gelatin (i.e., proteins) had the greatest negative effect on the electro-oxidation activity of urea, with decreases in peak current up to 80% compared to that of aurea-only solution. Further investigation of the binding mechanisms of the deleterious compounds using in situ ATR-FTIR spectroscopy revealed that urea and phosphate weakly bind to NiCo2O4 through hydrogen bonding or long-range forces, whereas creatinine interacts strongly, forming deactivating inner-sphere complexes. Phosphate is presumed to disrupt the interaction between urea and NiCo2O4 by serving as a hydrogen-bond acceptor in place of catalyst sites. The weak binding of urea supports the hypothesis that it is oxidized through an indirect electron transfer. Outcomes of this study contribute to the development of electrolytic systems for treating source-separated urine.